In the two examples below, a player must choose "either, or" in order to follow the card directions. (If this has been addressed elsewhere please point me in the right direction.)

In example #1 if a player has no cards in their hand MUST they reveal an additional encounter card since they have no cards to discard?

Similar situation in #2. If The One Ring has already been exhausted and the player can not choose to exhaust it MUST they search for a Nazgul enemy?

On the other hand, if the criteria of #1 or #2 can't be met, aka no cards to discard, or the ring has already been exhausted can a player disregard the When Revealed text?

#1

Morgul Orc

When Revealed: Either discard 1 random card from your hand, or reveal an additional encounter card.

#2

Call Of The Ring

When Revealed: The first player must choose: either search the encounter deck, discard pile, and victory display for a Nazgul enemy and add it to the staging area, or exhaust The One Ring and reveal the top card of the encounter deck

Does this help?

From the FAQ:

(1.44) “Must X or Y” vs “must either X or Y”

If a card instructs a player to perform one task or perform a second task using the structure “... must X or Y...” then the player must attempt to perform the first task, and performs the second task instead only if the first task cannot be performed. If a card instead uses the structure “... must either X or Y...” then the player may choose which task to perform, although one of them must be performed in full, if able.

So for effects that say "either", you get to choose, but if you can only perform one of them in full you have to pick that one.

Perfect thanks for the response.

The specific case of #2 is rather awkward because if you don't know the number of Nazgul in the quest you can't always tell before starting to resolve it whether you can resolve it in full or not.

When revealed text must always happen, if you don't have or play the card which cancels that effect directly, so if the ring is exhausted, you have to search for the Nazgul - that's plain and simple, same as #1 - if you can't (or won't) discard anything from your hand, do the other thing.